# Hydraulic Radius of a Pipe

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

Hydraulic radius, abbreviated as $$r_h$$, is the area cross-section of water in a pipe or channel divided by the wetting perimeter.

## Hydraulic radius of a Pipe formula

 $$\large{ r_h = \frac { A_c } { P_w } }$$

### Where:

 Units English Metric $$\large{ r_h }$$ = hydraulic radius $$\large{ in }$$ $$\large{ mm }$$ $$\large{ A_c }$$ = area cross-section of flow $$\large{ in^2 }$$ $$\large{ mm^2 }$$ $$\large{ P_w }$$ = wetting perimeter $$\large{ in }$$ $$\large{ mm }$$